Jon Sim scored on a broken play midway through the third period and Philadelphia hung on for a 2-1 victory in Providence on Wednesday and a 3-1 lead in the Eastern Conference championship series.
The Phantoms can return to the Calder Cup Finals for the first time since 1998 with a win in Game 5 on Friday.
R.J. Umberger‘s stick broke on a shot attempt from the point and the puck trickled to Sim, who fired it past an off-guard Hannu Toivonen with 10:10 left in regulation.
Antero Niittymaki did the rest, finishing with 34 saves on the night for the Phantoms. Toivonen stopped 29 shots for the Bruins.
John Slaney and Andy Hilbert traded power-play goals in the second period, but Providence could not convert on a late man-advantage with a chance to tie the score.